Reversing valve assembly



Feb. 29. 1944. c. J. SMITH 2,342,763

REVERSING VALVE ASSEMBLY Filed Aug. 6, 1942 29 2g gar $9.1.

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Patented Feb. 29, 1944 REVERSING VALVE ASSEMBLY Clarence J. Smith,Chicago, Ill., assignor to Brake Equipment & Supply (30., Chicago, Ill.,a corporation of Illinois Application August 6, 1942, Serial No. 453,877

Claims.

The present invention relates to a reversing piston valve assembly. I

An object of the invention is the provision of means for preventinginjury to the ends of the piston valve and particularly to the packingrings adjacent the ends thereof. In many instances over-travel of thepiston will cause it to strike the ends of the cylinder, and thisconstant impact causes the end ring flanges to be hammered down tightupon their respective rings. This objectionable feature is eliminated bythe present invention.

Another object is to provide a construction which will permit the pistonvalve to be easily and quickly removed from the cylinder for repair orreplacement.

A further object is the provision of means for effectively connectingthe piston valve to its operating rod. Often where a nut and boltstructure is utilized, the nut becomes loose, setting up lost motionbetween the valve and rod and eventually causing breakage of differentelements of the construction. This objectionable feature is alsoeliminated by the present construction.

With the foregoing and other objects in view, the invention will be morefully described, reference being had to the accompanying drawing, inwhich:

Figure 1 is a vertical section, showing the reversing piston valve inits uppermost position;

Figure 2 is a view somewhat similar to Figure 1, with the reversingvalve near the lower end of its stroke;

Figure 3 is an enlarged detail view of the piston, showing itsconnection to the reversing valve rod;

Figure 4 is a section taken on the line 4-4 of Figure 3, and

Figure 5 is a section taken on line 5-5 of Figure 1.

Referring now to the drawing and particularly to Figures 1 and 2, thereis disclosed a reversing piston valve assembly including a "casing orhead ID, a sleeve I I mounted in the casing and comprising the cylinderwithin which a piston valve I 2 reciprocates. This piston valve isprovided with top, bottom, and intermediate piston heads l3, l4 and I5,respectively, for controlling various ports leading to and from thecylinder I l.

The present assembly is particularly adapted for use with steam-drivenair compressors as used on railroad locomotives, but only the structureof the reversing piston valve is disclosed, since the compressorconstruction forms no part of the present invention. Only the portsleading to'and from the cylinder l I and controlled by the heads l3, l4and I5 are disclosed. In this connection, port or passage It leads tothe outer side of the large piston (not shown), while passage ll'leadsfrom the outer side of the large piston. The numeral l8 designates theexhaust passage, while l9 indicates the main steam supply chamber. Thepiston valve I2 is reciprocated by the usual plate on the steam piston(not shown) which strikes the shoulder 20 on the reversing valve rod 2|to move the reversing piston to its up position shown in Figure 1.Downward movement of, the aforementioned plate strikes the button 22 onthe lower end of the rod 20 to move the reversing piston 12 to itslowermost position shown in Figure 2.

During the reciprocation of the piston 12 which usually reverses atabout strokes per minute, the rod and valve have to withstandconsiderable pounding and unless preventative measures are taken, thetop and bottomring flanges 23 and 24 are distorted and hammered downtight upon their respective rings 25 and 25. In the present invention,this objectionable feature is eliminated by providing means forpreventing the flanges 23 and 24 from directly receiving the impact, ifthe piston over-travelsand strikes either end wall of the cylinder ll.

Referring to Figure 1, the top end wall of the cylinder comprises aseparate valve cap 27. This cap is externally threaded to engage threadsformed in the top of the opening in the casing or head I0 within whichthe sleeve or cylinder It is positioned. As clearly shown in Figures 1and 2, the cap bears upon the top end of the cylinder l i i" and forcesit against the shoulder portion 28 of the casing. However, if desired,the cap may clear the end of the cylinder, the latter in this instancebeing turned to a press fit in the casing Ill. The inner face of the cap27 is provided with a centrally disposed boss 29 which is surrounded byan annular groove or recess 30. The boss 29 is of such a diameter thatitwill contact the upper end of the piston l2 inwardly of the ring flange23. Furthermore, the groove or recess 30 is designed to register withthe peripheral edge or ring flange 23 of the upper end of the piston, asclearly shown in Figure 1. Thus, if th piston over-travels on itsupwardstroke, only the central portion thereof will engage the boss 29 and thetop ring flange 23 will register with the annular recess 30. In otherwords, the impact will be taken by the interior or centrally disposedportion of the upper end of the piston and not by the ring flange 23.Therefore, thefiange 23 will not be distorted or hammered downwardlyinto its ring 25.

Means are also provided to prevent the distortion or hammering of thelower ring flange 24 into its ring 25. It will be observed that the bodyof the cylinder or sleeve H is reduced adjacent its lower end by reasonof the shoulder 28 and that the extreme end portion thereof rests uponan annular shoulder 3! of the casing or head Ill. An annular opening 32is also formed in the lower portion of the head inwardly of the shoulder3| to permit movement of the reversing valve rod 2|. The diameter .ofthe opening 32 is somewhat larger than that of the rod 2| but is lessthan that of the piston head l4. In fact, the lower ring flange 24 islocated exteriorly of the opening 32. A boss 33 is formed on the lowerend of the piston 12 and extends to a point adjacent the inner end ofthe flange 24, The relative diameters of the opening 32 and boss 33 issuch that any over-travel of the piston on its downward movement willresult in the boss 33 engaging or contacting the shoulder 3| adjacentits inner annular edge. Thus, similarly to the arrangement at the upperend of the piston, any impact will be taken by the boss 33 interiorly oithe peripheral edge or flange 24, and thereby prevent distortion orhammering of this flange into its ring 26. As a result of the formationof the bosses 29 and 33, injury to the piston flanges and packing ringsis prevented, in the event that the piston should over-travel during itsoperation in the cylinder l I.

Referring to Figure 1, it will be observed that the piston is providedwith a centrally disposed passage 34 extending therethrough and normallypermitting flow of fluid from one end of the piston to the other. Itwill be observed that the 7 piston is of relatively small diameter, andthat the piston rod does not extend therethrough, so that the opening 34can be disposed centrally of the piston, as distinguished from that typein which. the piston rod extends through the center of the piston andthe fluid passage is laterally offset from the longitudinal axis of thepiston, This is of distinct advantage where the compressor is convertedfrom the old slide valve type to the piston type and it becomesessential or desirable to have a small piston. The upper end of thispassage is slightly enlarged and tapped to provide a threaded section35. The threaded area is formed so that a standard-sized bolt (notshown) may be easily screwed into the end of the piston to permitremoval of the same for repair or replacement. With this construction,and assuming that it is desired to remove the piston it, it is merelynecessary to unscrew the cap 21', crew a standard-sized bolt into thethreaded section 35, and pull out the piston from the cylinder H. Thisarrangement eliminates the necessity of removing the piston by means ofa pair of pliers or some other special puller.

The piston rod 2| is subjected to considerable pounding, and should bemade of a higher grade of material than is necessary for the piston, sothat it is desirable to form the piston and piston rod separately. It isessential, however, that the piston and rod be very securely joined, inorder that the shock of operation will not result in separating them. Inorder to prevent loosening of the rod 21 with respect to the piston Hand thus setting up lost motion between these members which wouldeventually cause breakage of some ofthe parts, the present invention isprovided with means for efiectively connecting these members to preventaccidental loosening or unthreading of the rod 2| from the lower end ofthe piston. Referring particularly to Figures 1 and 3, it will beobserved that the lower end of the piston i2 is provided with a reducedsection 36 which, on the downward stroke of the piston will enter theaperture 32, there being sufiicient clearance between the wall of thereduced section 33 to permit this, while at the same time the boss 33 onthe lower end of the piston will engage the annular shoulder 3| of thecasing of head If! and guard against hammering the ring flange 24, thuspreventing ring binding. This section is internally threaded andreceives the reduced externally threaded end portion 3'! of the rod 2!which closes the lower end'of the fluid pressure passage 34 disposedcentrally of the piston. In order to maintain communication with thatthrough passage 34, I provide the reduced section 33 of the piston withthe laterally disposed passages 42 disposed just below the lower pistonhead, as shown in Figures I, 3, and 4. This rod is provided with ashoulder 38 at the bottom of the threaded area, which shoulder contactsthe lower end of the reduced section 33 when the rod is screwed into thepiston and serves as a firm abutment for the lower end of the reducedsection 36 of the piston. The section 33 is provided with alignedopenings 38 which are adapted to register with an opening 4i! extendingtransversely through the threaded end portion 3'! of the rod. After therod has been screwed into the end section 36 and the holes or openings39 and 40 aligned, a pin or rivet 4! is inserted in these openings andthen enlarged or riveted over the ends of the pin to secure the partstogether and prevent unscrewing of the portions 36 and 31. It will beobserved that the holding means, that is, the rivet pin 4!, must bedisposed so that there will be no interference with the reduced section36 passing into the opening 32 in the casing, and for this reason thepin rivet 3! is headed down flush with the outer wall of the reducedsection 36. This effectively locks the piston :32 and rod 2! together,and prevents loosening of these members and subsequent injury to thedifferent elements of the reversing valve structure.

It is to be understood that the construction shown and described ismerely an illustration of the preferred embodiments and that suchchanges may be made as fall within the purview of one skilled in the artwithout departing from the spirit of the invention and the scope of theappended claims.

I claim:

1. In a reversing valve assembly, a casing, a

cylinder in said casing having an open end to permit piston removal, aremovable valve cap threaded in said casing to close the open end ofsaid cylinder, a piston valve having a longitudinal passage therethroughthreaded at its upper and lower ends and movable in said cylinder, areduced section at the lower end of said piston valve having lateralpassages disposed above the threaded lower end of the longitudinalpassage and communicating therewith, and a collared and threaded pistonrod seated against and engaging the lower threaded end of saidlongitudinal piston passage.

2. In a reversing valve assembly, a casing, a cylinder in said casinghaving an open end to permit piston removal, a removable valve capthreaded in said casing to close the open end of said. cylinder, apiston valve having a longitudinal passage therethrough threadedat itsupper and lower ends and movable in said cylinder, a reduced section atthe lower end of said piston valve having lateral passages disposedabove the threaded lower end of the longitudinal passage andcommunicating therewith, a collared and threaded piston rod seatedagainst and engaging the lower threaded end of said longitudinal pistonpassage, and a transversely disposed pin positively to lock said reducedpiston section and said piston rod together.

3. A piston valve and rod for a reversing valve assembly comprising apiston valve having a longitudinal fluid passage therethrough threadedat its upper and lower ends, a reduced section at the lower end of saidpiston valve having laterally disposed passages above the lower threadedend of the longitudinal fluid passage and communicating with saidlongitudinal passage, and a threaded piston rod engaging the threadedlower end of the longitudinal piston valve passage.

4. A piston valve and rod for a reversing valve assembly comprising apiston valve having a lonits upper and lower ends, a reduced section atthe lower end of said piston valve having laterally disposed passagesabove the lower threaded end of the longitudinal fluid passage andcommunicating with said longitudinal passage, a threaded piston rodengaging the threaded lower end of the longitudinal piston valvepassage, and a transversely disposed riveted pin positively to lock thethreaded end of said piston rod in place.

CLARENCE J. SMITH.

